The present invention relates to a reference voltage generating device and a method for reducing dissipation current in the normal operation.
In the conventional technique, a reference voltage generating device shown FIG. 1 is well known. Such reference voltage generating device has an operational amplifier 101, resistors R11, R12 for determining value of a feedback voltage which is supplied to the operational amplifier 101, and a capacitor C10 for the sake that it causes the reference voltage to be stabilized, which reference voltage is an output voltage of the operational amplifier.
The operational amplifier 101 inputs therein an external reference voltage xe2x80x98VREFOxe2x80x99. The external reference voltage is generated in such a way that difference of threshold value voltage between two different kinds of transistors, or the like. Thus, difference of threshold value voltage of two kinds of transistors is utilized for the sake of the external reference voltage. The external reference voltage is an external voltage which is generated while utilizing difference of threshold value voltage of two kinds of different transistors, therefore, the external reference voltage xe2x80x98VREFOxe2x80x99 is a fixed voltage independent on temperature or so forth. The reference voltage generating device outputs a reference voltage xe2x80x98VREFxe2x80x99. The xe2x80x98VREFxe2x80x99 denotes reference voltage. Relationship between the external reference voltage xe2x80x98VREFOxe2x80x99 and the reference voltage xe2x80x98VREFxe2x80x99 as being an output voltage of the reference voltage generating device is VREF=VREFOxc3x97(R11+R12)/R12. Such reference voltage xe2x80x98VREFxe2x80x99 becomes for instance, a standard of internal power-supply voltage.
Further, as the conventional technique, the official report of the Japanese Patent Application Laid-Open No. HEI 9-288897 discloses this kind of xe2x80x9cReference Voltage Generating Devicexe2x80x9d. The xe2x80x9cReference Voltage Generating Devicexe2x80x9d disclosed in the official report of the Japanese Patent Application Laid-Open No. HEI 9-288897 includes an operation signal generator which generates a pump enable signal to control operation of an oscillator, a comparator, and a reference voltage generator. At the time of normal operation, the operation signal generator generates an active pump enable signal to operate a voltage supply circuit. Thus, the voltage supply circuit generates voltage in answer to the reference voltage generated according to the reference voltage generator. At the time of standby, a CPU outputs an internal clock signal. The operation signal generator generates the active pump enable signal during a prescribed time interval from a leading edge of the clock signal according to such the internal clock signal from the CPU. The reference voltage generating device causes the voltage supply circuit to be operated intermittently in order to supply voltage.
However, in the conventional reference voltage generating device shown in FIG. 1, the reference voltage xe2x80x98VREFxe2x80x99 is normally inputted to a gate of a transistor. Thus, the gate of the transistor does not consume current. However, there is the problem that the dissipation current becomes large. In the above construction, the terminal of the reference voltage xe2x80x9cVREFxe2x80x9d is connected to ground through the resistors R11, R12, so that the operational amplifier 101 always should supply electric charge from the operational amplifier 101. Furthermore, the operational amplifier 101 itself consumes current, thus dissipation current becomes large.
Moreover, in the reference voltage generating device disclosed in the official report of the Japanese Patent Application Laid-Open No. HEI 9-288897, the reference voltage generating device causes the voltage supply circuit to be operated intermittently only at the time of standby. While at the time of normal operation, the reference voltage generating device causes the voltage supply circuit not to operate intermittently, therefore, there is the problem that the dissipation current becomes large.
In view of the foregoing, it is an object of the present invention, in order to overcome the above mentioned problems, to provide a reference voltage generating device and generating method of the same which enables consumption current to be reduced at the time of normal operation.
According to a first aspect of the present invention, in order to achieve the above mentioned object, there is provided a reference voltage generating device which is provided with an operational amplifier which comprises an intermittent operating means for operating the operational amplifier intermittently only during a prescribed time interval.
According to a second aspect of the present invention, in the first aspect, there is provided a reference voltage generating device, wherein the intermittent operating means comprises by an oscillator.
According to a third aspect of the present invention, there is provided a reference voltage generating device which comprises an operational amplifier which has an enable terminal, two resistors for determining a feedback voltage which is supplied to the operational amplifier, a transistor for deciding whether or not a route of the feedback voltage to be disconnected occurs, a capacitor for stabilizing reference voltage, which is an output voltage of the operational amplifier, and an intermittent operating means for providing a drive voltage in order to operate the operational amplifier intermittently, which intermittent operating means is provided at the enable terminal of the operational amplifier.
According to a fourth aspect of the present invention, in the third aspect, there is provided a reference voltage generating device, wherein the intermittent operating means comprises an oscillator.
According to a fifth aspect of the present invention, there is provided a reference voltage generating method of a reference voltage generating device provided with an operational amplifier which comprises the step of operating the operational amplifier intermittently only during a prescribed time interval by means of intermittent operating means.
According to a sixth aspect of the present invention, there is provided a reference voltage generating method of a reference voltage generating device provided with an operational amplifier which comprises the step of operating the operational amplifier intermittently only during a prescribed time interval by means of an oscillator.
According to a seventh aspect of the present invention, there is provided a reference voltage generating method of a reference voltage generating device which is provided with an operational amplifier which has an enable terminal, two resistors for determining a feedback voltage which is supplied to the operational amplifier, a transistor for deciding whether or not a route of the feedback voltage to be disconnected occurs, and a capacitor for stabilizing a reference voltage which is an output voltage of the operational amplifier, which comprises the step of providing a drive voltage in order to operate the operational amplifier intermittently by intermittent operating means provided at an enable terminal of the operational amplifier.
According to an eighth aspect of the present invention, there is provided a reference voltage generating method of a reference voltage generating device which is provided with an operational amplifier which has an enable terminal, two resistors for determining a feedback voltage which is supplied to the operational amplifier, a transistor for deciding whether or not a route of the feedback voltage to be disconnected occurs, and a capacitor for stabilizing a reference voltage which is an output voltage of the operational amplifier, which comprises the step of providing a drive voltage in order to operate the operational amplifier intermittently by an oscillator provided at an enable terminal of the operational amplifier.
The above and further objects and novel features of the invention will be more fully understood from the following detailed description when the same is read in connection with the accompanying drawings. It should be expressly understood, however, that the drawings are for purpose of illustration only and are not intended as a definition of the limits of the invention.